Question

我正在制作一个简单的待办事项列表应用。我已经完成了Apple Develop tutroial（https://developer.apple.com/library/ios/referencelibrary/GettingStarted/RoadMapiOS/FirstTutorial.html#//apple_ref/doc/uid/TP40011343-CH3-SW1）。现在，我正在尝试将此应用程序开发为功能齐全的应用程序。我的第一个目标是能够删除表格视图单元格。我正在使用此代码来获取删除按钮:(我正在使用Xcode 6）

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {
    if (editingStyle == UITableViewCellEditingStyleDelete) {
        [tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationFade];
    } else if (editingStyle == UITableViewCellEditingStyleInsert) {
        // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
    }
}

这使用户可以在单元格上从右向左拖动，并显示删除按钮。但是，在点击按钮时，应用程序崩溃了。异常断点显示此行导致错误。

我在网上搜索解决方案，我知道这种方法值得一看：

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {

    return [self.toDoItems count];
}

此外，其他一些答案说明了一个方法中的begin-和endUpdates。如果有人发现问题，我会很高兴的！

以下是表格视图的完整代码：

#import "XYZToDoListTableViewController.h"
#import "XYZToDoItem.h"
#import "XYZAddToDoItemViewController.h"

@interface XYZToDoListTableViewController ()

@property NSMutableArray *toDoItems;

@end

@implementation XYZToDoListTableViewController

- (void) loadInitialData {
    XYZToDoItem *item1 = [[XYZToDoItem alloc] init];
    item1.itemName = @"Add to-do item";
    [self.toDoItems addObject:item1];
    XYZToDoItem *item2 = [[XYZToDoItem alloc] init];
    item2.itemName = @"Do your job";
    [self.toDoItems addObject:item2];
    XYZToDoItem *item3 = [[XYZToDoItem alloc] init];
    item3.itemName = @"Mark item as completed";
    [self.toDoItems addObject:item3];
}

- (IBAction)unwindToList:(UIStoryboardSegue *)segue
{
    XYZAddToDoItemViewController *source = [segue sourceViewController];
    XYZToDoItem *item = source.toDoItem;
    if (item != nil) {
        [self.toDoItems addObject:item];
        [self.tableView  reloadData];
    }
}

- (void)viewDidLoad {
    [super viewDidLoad];
    self.toDoItems = [[NSMutableArray alloc] init];
    [self loadInitialData];
}

    // Uncomment the following line to preserve selection between presentations.
    // self.clearsSelectionOnViewWillAppear = NO;

    // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
    // self.navigationItem.rightBarButtonItem = self.editButtonItem;


- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

#pragma mark - Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {


     return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {

     return [self.toDoItems count];
}

/*
// Override to support conditional editing of the table view.
- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath {
    // Return NO if you do not want the specified item to be editable.
    return YES;
}
*/


- (void)tableView:(UITableView *)tableView commitEditingStyle: (UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {
    if (editingStyle == UITableViewCellEditingStyleDelete) {
        [tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationFade];
    } else if (editingStyle == UITableViewCellEditingStyleInsert) {
        // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
    }
}


/*
// Override to support rearranging the table view.
- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath {
}
*/

/*
// Override to support conditional rearranging of the table view.
- (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath {
    // Return NO if you do not want the item to be re-orderable.
     return YES;
}
*/

/*
#pragma mark - Navigation

// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    // Get the new view controller using [segue destinationViewController].
    // Pass the selected object to the new view controller.
}
*/

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
     UITableViewCell *cell = [tableView
                         dequeueReusableCellWithIdentifier:@"ListPrototypeCell" forIndexPath:indexPath];
    XYZToDoItem *toDoItem = [self.toDoItems objectAtIndex:indexPath.row];
     cell.textLabel.text = toDoItem.itemName;
    if (toDoItem.completed) {
        cell.accessoryType = UITableViewCellAccessoryCheckmark;
    } else {
        cell.accessoryType = UITableViewCellAccessoryNone;

    }
     return cell;
}


# pragma mark - Table view delegate

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    [tableView deselectRowAtIndexPath:indexPath animated:NO];
    XYZToDoItem *tappedItem  = [self.toDoItems objectAtIndex:indexPath.row];
    tappedItem.completed = !tappedItem.completed;
    [tableView reloadRowsAtIndexPaths:@[indexPath]withRowAnimation:UITableViewRowAnimationNone];
}

@end

非常感谢！（如果您需要更多代码，请立即让我！）

Answer 1

当你删除单元格时，你需要从你的数组中删除这一行，在你的情况下从self.toDoItems

[tableView beginUpdates];
[self.toDoItems removeObjectAtIndex: indexPath.row];
[tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationFade];
[tableView endUpdates];

删除表格视图单元格按钮崩溃

1 个答案: